全新java初学者实践教程6(Java SE5.0版)
dso6ZRx 基本语法3
lX^yd5M&f p.(8e kh V`F]L^m=L 我们这个教程侧重的是实践的内容和语言的重点。在[font="Times]java语言中还有很多细节的东西,请参考[font="Times]sun公司的官方培训教程。我们这里不能一一讲述。这节课我们来给大家提供一些程序流程控制的一些例子供大家学习。计算机怎么做事情,是我们教给他的。我们用它解决实际生活中的问题,所以计算机要描述现实生活中的流程。[font="Times]Java语言中提供了[font="Times]4类程序控制语句,来描述流程:
nE$8-*BZ_ TqzL] 'NS+ [font="Times] 1.循环语句[font="Times]:while,do-while,for
ZCdlTdY .UxbwTup [font="Times]2.分支语句[font="Times]:if-else,switch,
O=2"t%Gc [font="Times]
8ZmU(m 3.跳转语句[font="Times] break,continue,label: 和[font="Times]return
S;pKL,d>r [font="Times]
A .]o&S} 4.异常处理语句[font="Times]:try-catch-finally,throw
[1OX:O| A1VbqA 实践:
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[font="Times] 1.循环语句
>_R,^iH" [font="Times] while 语句
F+%6?2J [font="Times]class While {
O+8]y4%5 [font="Times]public static void main(String args[]) {
lB7 V4 [font="Times]int n = 10;
]/G~ L [font="Times]while(n > 0) {
3>Ne_kY [font="Times]System.out.println("tick " + n);
IP#w [font="Times]n--;
|f9fq~'1e [font="Times]}
nSMw 5
[font="Times]}
eSAB :L,K [font="Times]}
d7g3VF<j [font="Times] do…while 语句
dm;C @.ML [font="Times] class DoWhile {
rn$LZE
% [font="Times]public static void main(String args[]) {
qFqK.u [font="Times]int n = 10;
e}F1ZJz [font="Times]do {
|j?iD [font="Times]System.out.println("tick " + n);
Z@Tb3N/[ [font="Times]n--;
G@Jl4iHug" [font="Times]} while(n > 0);
AeQIsrAHE [font="Times]}
lWiC$ [font="Times]}
!(%^Tg= 二者区别,[font="Times]do…while至少循环一次,而[font="Times]while的表达式要是为[font="Times]flase的话可以一次也不循环。再通俗一点,[font="Times]do…while就算是括号里的是[font="Times]flase,人家最少也能[font="Times]do一次。
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[font="Times] for语句
}&E'ox<S [font="Times] class ForTick {
@<n8?"{5S [font="Times]public static void main(String args[]) {
CLQE@kF; [font="Times]int n;
5V"Fy&}: [font="Times]for(n=10; n>0; n--)
~~8?|@V [font="Times]System.out.println("tick " + n);
P#gY-k&Nr [font="Times]}
VG)Y$S8.> [font="Times]}
0 It[Pa qG 与上面那两个的区别,[font="Times]for循环执行的次数是可以在执行之前确定的。通俗一点说吧,看这个例子[font="Times] for(n=10; n>0; n--)就是在括号里的时候,就已经知道要循环[font="Times]10次了。
e*nT+Rp 还有啊,[font="Times]for循环的部分可以为空的
In3},x+$ [font="Times]class ForVar {
@bkZ< Gq [font="Times]public static void main(String args[]) {
{c#{dT [font="Times]int i;
Y6&B%t<bo [font="Times]boolean done = false;
!F^j\ [font="Times]i = 0;
=|Q7k +b [font="Times]for( ; !done; ) {
X+R?>xq{=h [font="Times]System.out.println("i is " + i);
nQ\)~MKd [font="Times]if(i == 10) done = true;
L`iC?<} [font="Times]i++;
sKIpL(_I$ [font="Times]}
l^LYSZg'R8 [font="Times]}
uU|fCwQt [font="Times]}
循环语句的例子下载 &EZq%Sd [font="Times] 2.分支语句[font="Times]
W-72&\7 [font="Times] if/else语句
2c%*u {=: [font="Times]class IfElse {
J&vmW}& [font="Times]public static void main(String args[]) {
S4'\=w# [font="Times]int month = 4; // April
JQ[~N- [font="Times]String season;
G`Ix-dADJm [font="Times]if(month == 12 || month == 1 || month == 2)
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& [font="Times]season = "Winter";
sF+mfoMtG [font="Times]else if(month == 3 || month == 4 || month == 5)
T({]fc!c [font="Times]season = "Spring";
|=xK-;qs [font="Times]else if(month == 6 || month == 7 || month == 8)
Gtyy^tz[ [font="Times]season = "Summer";
)|d]0/< [font="Times]else if(month == 9 || month == 10 || month == 11)
=9LeFrz [font="Times]season = "Autumn";
cb9ndZ)v. [font="Times]else
5os(. [font="Times]season = "Bogus Month";
qYwEPGa\ [font="Times]System.out.println("April is in the " + season + ".");
?6m6 4{M [font="Times]}
cTq}H_hC [font="Times]}
*8a8Ng [font="Times]//这段程序输出[font="Times]:
nc0!ag [font="Times]//April is in the Spring.
e2P
ds` [font="Times]// 注意[font="Times] “[font="Times]||”是或运算
_xHEA2e! [font="Times] switch语句
m\XgvpvrP [font="Times] class Switch {
M^e;WY@ D [font="Times]public static void main(String args[]) {
t9!8Bh< [font="Times]int month = 4;
7*a']W{aJ [font="Times]String season;
5Az4 < [font="Times]switch (month) {
;I#f:UQ [font="Times]case 12:
M?3Nh; [font="Times]case 1:
@N?u{|R:d [font="Times]case 2:
]csfK${ [font="Times]season = "Winter";
\dq}nOsX* [font="Times]break;
"< c,I=A [font="Times]case 3:
A<+veqb4 [font="Times]case 4:
?xb4y=P7 [font="Times]case 5:
wcd1.$ n [font="Times]season = "Spring";
7M#irCX [font="Times]break;
F/QRgXV [font="Times]case 6:
l1EI4Y9KG [font="Times]case 7:
N
N1(f [font="Times]case 8:
j3J\%7^i [font="Times]season = "Summer";
Q`ALyp,9b [font="Times]break;
Lwzk<+>w^ [font="Times]case 9:
E &wz0d;gf [font="Times]case 10:
Pf 4b/w/ [font="Times]case 11:
$N[R99*x8 [font="Times]season = "Autumn";
Avc9W[4 [font="Times]break;
;:%*h2 [font="Times]default:
fBi6%
#
[font="Times]season = "Bogus Month";
pI>[^7 [font="Times]}
';\v:dP [font="Times]System.out.println("April is in the " + season + ".");
_T{
"F [font="Times]}
uE}A-\G [font="Times]}
分支语句代码下载 %:DH_0 $&C~Qti|G [font="Times]switch语句适合于条件非常多的逻辑
mHY R? 请看上述语句可以混合使用,请看
下载例子